[T106][ZXW-22]7520V3SCV2.01.01.02P42U09_VEC_V0.8_AP_VEC origin source commit
Change-Id: Ic6e05d89ecd62fc34f82b23dcf306c93764aec4b
diff --git a/ap/os/linux/linux-3.4.x/block/elevator.c b/ap/os/linux/linux-3.4.x/block/elevator.c
new file mode 100644
index 0000000..92baf6b
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/block/elevator.c
@@ -0,0 +1,1065 @@
+/*
+ * Block device elevator/IO-scheduler.
+ *
+ * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
+ *
+ * 30042000 Jens Axboe <axboe@kernel.dk> :
+ *
+ * Split the elevator a bit so that it is possible to choose a different
+ * one or even write a new "plug in". There are three pieces:
+ * - elevator_fn, inserts a new request in the queue list
+ * - elevator_merge_fn, decides whether a new buffer can be merged with
+ * an existing request
+ * - elevator_dequeue_fn, called when a request is taken off the active list
+ *
+ * 20082000 Dave Jones <davej@suse.de> :
+ * Removed tests for max-bomb-segments, which was breaking elvtune
+ * when run without -bN
+ *
+ * Jens:
+ * - Rework again to work with bio instead of buffer_heads
+ * - loose bi_dev comparisons, partition handling is right now
+ * - completely modularize elevator setup and teardown
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/compiler.h>
+#include <linux/blktrace_api.h>
+#include <linux/hash.h>
+#include <linux/uaccess.h>
+
+#include <trace/events/block.h>
+
+#include "blk.h"
+
+static DEFINE_SPINLOCK(elv_list_lock);
+static LIST_HEAD(elv_list);
+
+/*
+ * Merge hash stuff.
+ */
+static const int elv_hash_shift = 6;
+#define ELV_HASH_BLOCK(sec) ((sec) >> 3)
+#define ELV_HASH_FN(sec) \
+ (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift))
+#define ELV_HASH_ENTRIES (1 << elv_hash_shift)
+#define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq))
+
+/*
+ * Query io scheduler to see if the current process issuing bio may be
+ * merged with rq.
+ */
+static int elv_iosched_allow_merge(struct request *rq, struct bio *bio)
+{
+ struct request_queue *q = rq->q;
+ struct elevator_queue *e = q->elevator;
+
+ if (e->type->ops.elevator_allow_merge_fn)
+ return e->type->ops.elevator_allow_merge_fn(q, rq, bio);
+
+ return 1;
+}
+
+/*
+ * can we safely merge with this request?
+ */
+bool elv_rq_merge_ok(struct request *rq, struct bio *bio)
+{
+ if (!blk_rq_merge_ok(rq, bio))
+ return 0;
+
+ if (!elv_iosched_allow_merge(rq, bio))
+ return 0;
+
+ return 1;
+}
+EXPORT_SYMBOL(elv_rq_merge_ok);
+
+static struct elevator_type *elevator_find(const char *name)
+{
+ struct elevator_type *e;
+
+ list_for_each_entry(e, &elv_list, list) {
+ if (!strcmp(e->elevator_name, name))
+ return e;
+ }
+
+ return NULL;
+}
+
+static void elevator_put(struct elevator_type *e)
+{
+ module_put(e->elevator_owner);
+}
+
+static struct elevator_type *elevator_get(const char *name)
+{
+ struct elevator_type *e;
+
+ spin_lock(&elv_list_lock);
+
+ e = elevator_find(name);
+ if (!e) {
+ spin_unlock(&elv_list_lock);
+ request_module("%s-iosched", name);
+ spin_lock(&elv_list_lock);
+ e = elevator_find(name);
+ }
+
+ if (e && !try_module_get(e->elevator_owner))
+ e = NULL;
+
+ spin_unlock(&elv_list_lock);
+
+ return e;
+}
+
+static int elevator_init_queue(struct request_queue *q,
+ struct elevator_queue *eq)
+{
+ eq->elevator_data = eq->type->ops.elevator_init_fn(q);
+ if (eq->elevator_data)
+ return 0;
+ return -ENOMEM;
+}
+
+static char chosen_elevator[ELV_NAME_MAX];
+
+static int __init elevator_setup(char *str)
+{
+ /*
+ * Be backwards-compatible with previous kernels, so users
+ * won't get the wrong elevator.
+ */
+ strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
+ return 1;
+}
+
+__setup("elevator=", elevator_setup);
+
+static struct kobj_type elv_ktype;
+
+static struct elevator_queue *elevator_alloc(struct request_queue *q,
+ struct elevator_type *e)
+{
+ struct elevator_queue *eq;
+ int i;
+
+ eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node);
+ if (unlikely(!eq))
+ goto err;
+
+ eq->type = e;
+ kobject_init(&eq->kobj, &elv_ktype);
+ mutex_init(&eq->sysfs_lock);
+
+ eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES,
+ GFP_KERNEL, q->node);
+ if (!eq->hash)
+ goto err;
+
+ for (i = 0; i < ELV_HASH_ENTRIES; i++)
+ INIT_HLIST_HEAD(&eq->hash[i]);
+
+ return eq;
+err:
+ kfree(eq);
+ elevator_put(e);
+ return NULL;
+}
+
+static void elevator_release(struct kobject *kobj)
+{
+ struct elevator_queue *e;
+
+ e = container_of(kobj, struct elevator_queue, kobj);
+ elevator_put(e->type);
+ kfree(e->hash);
+ kfree(e);
+}
+
+int elevator_init(struct request_queue *q, char *name)
+{
+ struct elevator_type *e = NULL;
+ struct elevator_queue *eq;
+ int err;
+
+ if (unlikely(q->elevator))
+ return 0;
+
+ INIT_LIST_HEAD(&q->queue_head);
+ q->last_merge = NULL;
+ q->end_sector = 0;
+ q->boundary_rq = NULL;
+
+ if (name) {
+ e = elevator_get(name);
+ if (!e)
+ return -EINVAL;
+ }
+
+ if (!e && *chosen_elevator) {
+ e = elevator_get(chosen_elevator);
+ if (!e)
+ printk(KERN_ERR "I/O scheduler %s not found\n",
+ chosen_elevator);
+ }
+
+ if (!e) {
+ e = elevator_get(CONFIG_DEFAULT_IOSCHED);
+ if (!e) {
+ printk(KERN_ERR
+ "Default I/O scheduler not found. " \
+ "Using noop.\n");
+ e = elevator_get("noop");
+ if (unlikely(!e))
+ return -ENOENT;
+ }
+ }
+
+ eq = elevator_alloc(q, e);
+ if (!eq)
+ return -ENOMEM;
+
+ err = elevator_init_queue(q, eq);
+ if (err) {
+ kobject_put(&eq->kobj);
+ return err;
+ }
+
+ q->elevator = eq;
+ return 0;
+}
+EXPORT_SYMBOL(elevator_init);
+
+void elevator_exit(struct elevator_queue *e)
+{
+ mutex_lock(&e->sysfs_lock);
+ if (e->type->ops.elevator_exit_fn)
+ e->type->ops.elevator_exit_fn(e);
+ mutex_unlock(&e->sysfs_lock);
+
+ kobject_put(&e->kobj);
+}
+EXPORT_SYMBOL(elevator_exit);
+
+static inline void __elv_rqhash_del(struct request *rq)
+{
+ hlist_del_init(&rq->hash);
+}
+
+static void elv_rqhash_del(struct request_queue *q, struct request *rq)
+{
+ if (ELV_ON_HASH(rq))
+ __elv_rqhash_del(rq);
+}
+
+static void elv_rqhash_add(struct request_queue *q, struct request *rq)
+{
+ struct elevator_queue *e = q->elevator;
+
+ BUG_ON(ELV_ON_HASH(rq));
+ hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
+}
+
+static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
+{
+ __elv_rqhash_del(rq);
+ elv_rqhash_add(q, rq);
+}
+
+static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
+{
+ struct elevator_queue *e = q->elevator;
+ struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
+ struct hlist_node *entry, *next;
+ struct request *rq;
+
+ hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
+ BUG_ON(!ELV_ON_HASH(rq));
+
+ if (unlikely(!rq_mergeable(rq))) {
+ __elv_rqhash_del(rq);
+ continue;
+ }
+
+ if (rq_hash_key(rq) == offset)
+ return rq;
+ }
+
+ return NULL;
+}
+
+/*
+ * RB-tree support functions for inserting/lookup/removal of requests
+ * in a sorted RB tree.
+ */
+void elv_rb_add(struct rb_root *root, struct request *rq)
+{
+ struct rb_node **p = &root->rb_node;
+ struct rb_node *parent = NULL;
+ struct request *__rq;
+
+ while (*p) {
+ parent = *p;
+ __rq = rb_entry(parent, struct request, rb_node);
+
+ if (blk_rq_pos(rq) < blk_rq_pos(__rq))
+ p = &(*p)->rb_left;
+ else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
+ p = &(*p)->rb_right;
+ }
+
+ rb_link_node(&rq->rb_node, parent, p);
+ rb_insert_color(&rq->rb_node, root);
+}
+EXPORT_SYMBOL(elv_rb_add);
+
+void elv_rb_del(struct rb_root *root, struct request *rq)
+{
+ BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
+ rb_erase(&rq->rb_node, root);
+ RB_CLEAR_NODE(&rq->rb_node);
+}
+EXPORT_SYMBOL(elv_rb_del);
+
+struct request *elv_rb_find(struct rb_root *root, sector_t sector)
+{
+ struct rb_node *n = root->rb_node;
+ struct request *rq;
+
+ while (n) {
+ rq = rb_entry(n, struct request, rb_node);
+
+ if (sector < blk_rq_pos(rq))
+ n = n->rb_left;
+ else if (sector > blk_rq_pos(rq))
+ n = n->rb_right;
+ else
+ return rq;
+ }
+
+ return NULL;
+}
+EXPORT_SYMBOL(elv_rb_find);
+
+/*
+ * Insert rq into dispatch queue of q. Queue lock must be held on
+ * entry. rq is sort instead into the dispatch queue. To be used by
+ * specific elevators.
+ */
+void elv_dispatch_sort(struct request_queue *q, struct request *rq)
+{
+ sector_t boundary;
+ struct list_head *entry;
+ int stop_flags;
+
+ if (q->last_merge == rq)
+ q->last_merge = NULL;
+
+ elv_rqhash_del(q, rq);
+
+ q->nr_sorted--;
+
+ boundary = q->end_sector;
+ stop_flags = REQ_SOFTBARRIER | REQ_STARTED;
+ list_for_each_prev(entry, &q->queue_head) {
+ struct request *pos = list_entry_rq(entry);
+
+ if ((rq->cmd_flags & REQ_DISCARD) !=
+ (pos->cmd_flags & REQ_DISCARD))
+ break;
+ if (rq_data_dir(rq) != rq_data_dir(pos))
+ break;
+ if (pos->cmd_flags & stop_flags)
+ break;
+ if (blk_rq_pos(rq) >= boundary) {
+ if (blk_rq_pos(pos) < boundary)
+ continue;
+ } else {
+ if (blk_rq_pos(pos) >= boundary)
+ break;
+ }
+ if (blk_rq_pos(rq) >= blk_rq_pos(pos))
+ break;
+ }
+
+ list_add(&rq->queuelist, entry);
+}
+EXPORT_SYMBOL(elv_dispatch_sort);
+
+/*
+ * Insert rq into dispatch queue of q. Queue lock must be held on
+ * entry. rq is added to the back of the dispatch queue. To be used by
+ * specific elevators.
+ */
+void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
+{
+ if (q->last_merge == rq)
+ q->last_merge = NULL;
+
+ elv_rqhash_del(q, rq);
+
+ q->nr_sorted--;
+
+ q->end_sector = rq_end_sector(rq);
+ q->boundary_rq = rq;
+ list_add_tail(&rq->queuelist, &q->queue_head);
+}
+EXPORT_SYMBOL(elv_dispatch_add_tail);
+
+int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
+{
+ struct elevator_queue *e = q->elevator;
+ struct request *__rq;
+ int ret;
+
+ /*
+ * Levels of merges:
+ * nomerges: No merges at all attempted
+ * noxmerges: Only simple one-hit cache try
+ * merges: All merge tries attempted
+ */
+ if (blk_queue_nomerges(q))
+ return ELEVATOR_NO_MERGE;
+
+ /*
+ * First try one-hit cache.
+ */
+ if (q->last_merge && elv_rq_merge_ok(q->last_merge, bio)) {
+ ret = blk_try_merge(q->last_merge, bio);
+ if (ret != ELEVATOR_NO_MERGE) {
+ *req = q->last_merge;
+ return ret;
+ }
+ }
+
+ if (blk_queue_noxmerges(q))
+ return ELEVATOR_NO_MERGE;
+
+ /*
+ * See if our hash lookup can find a potential backmerge.
+ */
+ __rq = elv_rqhash_find(q, bio->bi_sector);
+ if (__rq && elv_rq_merge_ok(__rq, bio)) {
+ *req = __rq;
+ return ELEVATOR_BACK_MERGE;
+ }
+
+ if (e->type->ops.elevator_merge_fn)
+ return e->type->ops.elevator_merge_fn(q, req, bio);
+
+ return ELEVATOR_NO_MERGE;
+}
+
+/*
+ * Attempt to do an insertion back merge. Only check for the case where
+ * we can append 'rq' to an existing request, so we can throw 'rq' away
+ * afterwards.
+ *
+ * Returns true if we merged, false otherwise
+ */
+static bool elv_attempt_insert_merge(struct request_queue *q,
+ struct request *rq)
+{
+ struct request *__rq;
+
+ if (blk_queue_nomerges(q))
+ return false;
+
+ /*
+ * First try one-hit cache.
+ */
+ if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
+ return true;
+
+ if (blk_queue_noxmerges(q))
+ return false;
+
+ /*
+ * See if our hash lookup can find a potential backmerge.
+ */
+ __rq = elv_rqhash_find(q, blk_rq_pos(rq));
+ if (__rq && blk_attempt_req_merge(q, __rq, rq))
+ return true;
+
+ return false;
+}
+
+void elv_merged_request(struct request_queue *q, struct request *rq, int type)
+{
+ struct elevator_queue *e = q->elevator;
+
+ if (e->type->ops.elevator_merged_fn)
+ e->type->ops.elevator_merged_fn(q, rq, type);
+
+ if (type == ELEVATOR_BACK_MERGE)
+ elv_rqhash_reposition(q, rq);
+
+ q->last_merge = rq;
+}
+
+void elv_merge_requests(struct request_queue *q, struct request *rq,
+ struct request *next)
+{
+ struct elevator_queue *e = q->elevator;
+ const int next_sorted = next->cmd_flags & REQ_SORTED;
+
+ if (next_sorted && e->type->ops.elevator_merge_req_fn)
+ e->type->ops.elevator_merge_req_fn(q, rq, next);
+
+ elv_rqhash_reposition(q, rq);
+
+ if (next_sorted) {
+ elv_rqhash_del(q, next);
+ q->nr_sorted--;
+ }
+
+ q->last_merge = rq;
+}
+
+void elv_bio_merged(struct request_queue *q, struct request *rq,
+ struct bio *bio)
+{
+ struct elevator_queue *e = q->elevator;
+
+ if (e->type->ops.elevator_bio_merged_fn)
+ e->type->ops.elevator_bio_merged_fn(q, rq, bio);
+}
+
+void elv_requeue_request(struct request_queue *q, struct request *rq)
+{
+ /*
+ * it already went through dequeue, we need to decrement the
+ * in_flight count again
+ */
+ if (blk_account_rq(rq)) {
+ q->in_flight[rq_is_sync(rq)]--;
+ if (rq->cmd_flags & REQ_SORTED)
+ elv_deactivate_rq(q, rq);
+ }
+
+ rq->cmd_flags &= ~REQ_STARTED;
+
+ __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
+}
+
+void elv_drain_elevator(struct request_queue *q)
+{
+ static int printed;
+
+ lockdep_assert_held(q->queue_lock);
+
+ while (q->elevator->type->ops.elevator_dispatch_fn(q, 1))
+ ;
+ if (q->nr_sorted && printed++ < 10) {
+ printk(KERN_ERR "%s: forced dispatching is broken "
+ "(nr_sorted=%u), please report this\n",
+ q->elevator->type->elevator_name, q->nr_sorted);
+ }
+}
+
+void elv_quiesce_start(struct request_queue *q)
+{
+ if (!q->elevator)
+ return;
+
+ spin_lock_irq(q->queue_lock);
+ queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
+ spin_unlock_irq(q->queue_lock);
+
+ blk_drain_queue(q, false);
+}
+
+void elv_quiesce_end(struct request_queue *q)
+{
+ spin_lock_irq(q->queue_lock);
+ queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
+ spin_unlock_irq(q->queue_lock);
+}
+
+void __elv_add_request(struct request_queue *q, struct request *rq, int where)
+{
+ trace_block_rq_insert(q, rq);
+
+ rq->q = q;
+
+ if (rq->cmd_flags & REQ_SOFTBARRIER) {
+ /* barriers are scheduling boundary, update end_sector */
+ if (rq->cmd_type == REQ_TYPE_FS ||
+ (rq->cmd_flags & REQ_DISCARD)) {
+ q->end_sector = rq_end_sector(rq);
+ q->boundary_rq = rq;
+ }
+ } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
+ (where == ELEVATOR_INSERT_SORT ||
+ where == ELEVATOR_INSERT_SORT_MERGE))
+ where = ELEVATOR_INSERT_BACK;
+
+ switch (where) {
+ case ELEVATOR_INSERT_REQUEUE:
+ case ELEVATOR_INSERT_FRONT:
+ rq->cmd_flags |= REQ_SOFTBARRIER;
+ list_add(&rq->queuelist, &q->queue_head);
+ break;
+
+ case ELEVATOR_INSERT_BACK:
+ rq->cmd_flags |= REQ_SOFTBARRIER;
+ elv_drain_elevator(q);
+ list_add_tail(&rq->queuelist, &q->queue_head);
+ /*
+ * We kick the queue here for the following reasons.
+ * - The elevator might have returned NULL previously
+ * to delay requests and returned them now. As the
+ * queue wasn't empty before this request, ll_rw_blk
+ * won't run the queue on return, resulting in hang.
+ * - Usually, back inserted requests won't be merged
+ * with anything. There's no point in delaying queue
+ * processing.
+ */
+ __blk_run_queue(q);
+ break;
+
+ case ELEVATOR_INSERT_SORT_MERGE:
+ /*
+ * If we succeed in merging this request with one in the
+ * queue already, we are done - rq has now been freed,
+ * so no need to do anything further.
+ */
+ if (elv_attempt_insert_merge(q, rq))
+ break;
+ case ELEVATOR_INSERT_SORT:
+ BUG_ON(rq->cmd_type != REQ_TYPE_FS &&
+ !(rq->cmd_flags & REQ_DISCARD));
+ rq->cmd_flags |= REQ_SORTED;
+ q->nr_sorted++;
+ if (rq_mergeable(rq)) {
+ elv_rqhash_add(q, rq);
+ if (!q->last_merge)
+ q->last_merge = rq;
+ }
+
+ /*
+ * Some ioscheds (cfq) run q->request_fn directly, so
+ * rq cannot be accessed after calling
+ * elevator_add_req_fn.
+ */
+ q->elevator->type->ops.elevator_add_req_fn(q, rq);
+ break;
+
+ case ELEVATOR_INSERT_FLUSH:
+ rq->cmd_flags |= REQ_SOFTBARRIER;
+ blk_insert_flush(rq);
+ break;
+ default:
+ printk(KERN_ERR "%s: bad insertion point %d\n",
+ __func__, where);
+ BUG();
+ }
+}
+EXPORT_SYMBOL(__elv_add_request);
+
+void elv_add_request(struct request_queue *q, struct request *rq, int where)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(q->queue_lock, flags);
+ __elv_add_request(q, rq, where);
+ spin_unlock_irqrestore(q->queue_lock, flags);
+}
+EXPORT_SYMBOL(elv_add_request);
+
+struct request *elv_latter_request(struct request_queue *q, struct request *rq)
+{
+ struct elevator_queue *e = q->elevator;
+
+ if (e->type->ops.elevator_latter_req_fn)
+ return e->type->ops.elevator_latter_req_fn(q, rq);
+ return NULL;
+}
+
+struct request *elv_former_request(struct request_queue *q, struct request *rq)
+{
+ struct elevator_queue *e = q->elevator;
+
+ if (e->type->ops.elevator_former_req_fn)
+ return e->type->ops.elevator_former_req_fn(q, rq);
+ return NULL;
+}
+
+int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
+{
+ struct elevator_queue *e = q->elevator;
+
+ if (e->type->ops.elevator_set_req_fn)
+ return e->type->ops.elevator_set_req_fn(q, rq, gfp_mask);
+ return 0;
+}
+
+void elv_put_request(struct request_queue *q, struct request *rq)
+{
+ struct elevator_queue *e = q->elevator;
+
+ if (e->type->ops.elevator_put_req_fn)
+ e->type->ops.elevator_put_req_fn(rq);
+}
+
+int elv_may_queue(struct request_queue *q, int rw)
+{
+ struct elevator_queue *e = q->elevator;
+
+ if (e->type->ops.elevator_may_queue_fn)
+ return e->type->ops.elevator_may_queue_fn(q, rw);
+
+ return ELV_MQUEUE_MAY;
+}
+
+void elv_abort_queue(struct request_queue *q)
+{
+ struct request *rq;
+
+ blk_abort_flushes(q);
+
+ while (!list_empty(&q->queue_head)) {
+ rq = list_entry_rq(q->queue_head.next);
+ rq->cmd_flags |= REQ_QUIET;
+ trace_block_rq_abort(q, rq);
+ /*
+ * Mark this request as started so we don't trigger
+ * any debug logic in the end I/O path.
+ */
+ blk_start_request(rq);
+ __blk_end_request_all(rq, -EIO);
+ }
+}
+EXPORT_SYMBOL(elv_abort_queue);
+
+void elv_completed_request(struct request_queue *q, struct request *rq)
+{
+ struct elevator_queue *e = q->elevator;
+
+ /*
+ * request is released from the driver, io must be done
+ */
+ if (blk_account_rq(rq)) {
+ q->in_flight[rq_is_sync(rq)]--;
+ if ((rq->cmd_flags & REQ_SORTED) &&
+ e->type->ops.elevator_completed_req_fn)
+ e->type->ops.elevator_completed_req_fn(q, rq);
+ }
+}
+
+#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
+
+static ssize_t
+elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
+{
+ struct elv_fs_entry *entry = to_elv(attr);
+ struct elevator_queue *e;
+ ssize_t error;
+
+ if (!entry->show)
+ return -EIO;
+
+ e = container_of(kobj, struct elevator_queue, kobj);
+ mutex_lock(&e->sysfs_lock);
+ error = e->type ? entry->show(e, page) : -ENOENT;
+ mutex_unlock(&e->sysfs_lock);
+ return error;
+}
+
+static ssize_t
+elv_attr_store(struct kobject *kobj, struct attribute *attr,
+ const char *page, size_t length)
+{
+ struct elv_fs_entry *entry = to_elv(attr);
+ struct elevator_queue *e;
+ ssize_t error;
+
+ if (!entry->store)
+ return -EIO;
+
+ e = container_of(kobj, struct elevator_queue, kobj);
+ mutex_lock(&e->sysfs_lock);
+ error = e->type ? entry->store(e, page, length) : -ENOENT;
+ mutex_unlock(&e->sysfs_lock);
+ return error;
+}
+
+static const struct sysfs_ops elv_sysfs_ops = {
+ .show = elv_attr_show,
+ .store = elv_attr_store,
+};
+
+static struct kobj_type elv_ktype = {
+ .sysfs_ops = &elv_sysfs_ops,
+ .release = elevator_release,
+};
+
+int __elv_register_queue(struct request_queue *q, struct elevator_queue *e)
+{
+ int error;
+
+ error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
+ if (!error) {
+ struct elv_fs_entry *attr = e->type->elevator_attrs;
+ if (attr) {
+ while (attr->attr.name) {
+ if (sysfs_create_file(&e->kobj, &attr->attr))
+ break;
+ attr++;
+ }
+ }
+ kobject_uevent(&e->kobj, KOBJ_ADD);
+ e->registered = 1;
+ }
+ return error;
+}
+
+int elv_register_queue(struct request_queue *q)
+{
+ return __elv_register_queue(q, q->elevator);
+}
+EXPORT_SYMBOL(elv_register_queue);
+
+void elv_unregister_queue(struct request_queue *q)
+{
+ if (q) {
+ struct elevator_queue *e = q->elevator;
+
+ kobject_uevent(&e->kobj, KOBJ_REMOVE);
+ kobject_del(&e->kobj);
+ e->registered = 0;
+ }
+}
+EXPORT_SYMBOL(elv_unregister_queue);
+
+int elv_register(struct elevator_type *e)
+{
+ char *def = "";
+
+ /* create icq_cache if requested */
+ if (e->icq_size) {
+ if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
+ WARN_ON(e->icq_align < __alignof__(struct io_cq)))
+ return -EINVAL;
+
+ snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
+ "%s_io_cq", e->elevator_name);
+ e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
+ e->icq_align, 0, NULL);
+ if (!e->icq_cache)
+ return -ENOMEM;
+ }
+
+ /* register, don't allow duplicate names */
+ spin_lock(&elv_list_lock);
+ if (elevator_find(e->elevator_name)) {
+ spin_unlock(&elv_list_lock);
+ if (e->icq_cache)
+ kmem_cache_destroy(e->icq_cache);
+ return -EBUSY;
+ }
+ list_add_tail(&e->list, &elv_list);
+ spin_unlock(&elv_list_lock);
+
+ /* print pretty message */
+ if (!strcmp(e->elevator_name, chosen_elevator) ||
+ (!*chosen_elevator &&
+ !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
+ def = " (default)";
+
+ printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
+ def);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(elv_register);
+
+void elv_unregister(struct elevator_type *e)
+{
+ /* unregister */
+ spin_lock(&elv_list_lock);
+ list_del_init(&e->list);
+ spin_unlock(&elv_list_lock);
+
+ /*
+ * Destroy icq_cache if it exists. icq's are RCU managed. Make
+ * sure all RCU operations are complete before proceeding.
+ */
+ if (e->icq_cache) {
+ rcu_barrier();
+ kmem_cache_destroy(e->icq_cache);
+ e->icq_cache = NULL;
+ }
+}
+EXPORT_SYMBOL_GPL(elv_unregister);
+
+/*
+ * switch to new_e io scheduler. be careful not to introduce deadlocks -
+ * we don't free the old io scheduler, before we have allocated what we
+ * need for the new one. this way we have a chance of going back to the old
+ * one, if the new one fails init for some reason.
+ */
+static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
+{
+ struct elevator_queue *old_elevator, *e;
+ int err;
+
+ /* allocate new elevator */
+ e = elevator_alloc(q, new_e);
+ if (!e)
+ return -ENOMEM;
+
+ err = elevator_init_queue(q, e);
+ if (err) {
+ kobject_put(&e->kobj);
+ return err;
+ }
+
+ /* turn on BYPASS and drain all requests w/ elevator private data */
+ elv_quiesce_start(q);
+
+ /* unregister old queue, register new one and kill old elevator */
+ if (q->elevator->registered) {
+ elv_unregister_queue(q);
+ err = __elv_register_queue(q, e);
+ if (err)
+ goto fail_register;
+ }
+
+ /* done, clear io_cq's, switch elevators and turn off BYPASS */
+ spin_lock_irq(q->queue_lock);
+ ioc_clear_queue(q);
+ old_elevator = q->elevator;
+ q->elevator = e;
+ spin_unlock_irq(q->queue_lock);
+
+ elevator_exit(old_elevator);
+ elv_quiesce_end(q);
+
+ blk_add_trace_msg(q, "elv switch: %s", e->type->elevator_name);
+
+ return 0;
+
+fail_register:
+ /*
+ * switch failed, exit the new io scheduler and reattach the old
+ * one again (along with re-adding the sysfs dir)
+ */
+ elevator_exit(e);
+ elv_register_queue(q);
+ elv_quiesce_end(q);
+
+ return err;
+}
+
+/*
+ * Switch this queue to the given IO scheduler.
+ */
+static int __elevator_change(struct request_queue *q, const char *name)
+{
+ char elevator_name[ELV_NAME_MAX];
+ struct elevator_type *e;
+
+ if (!q->elevator)
+ return -ENXIO;
+
+ strlcpy(elevator_name, name, sizeof(elevator_name));
+ e = elevator_get(strstrip(elevator_name));
+ if (!e) {
+ printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
+ return -EINVAL;
+ }
+
+ if (!strcmp(elevator_name, q->elevator->type->elevator_name)) {
+ elevator_put(e);
+ return 0;
+ }
+
+ return elevator_switch(q, e);
+}
+
+int elevator_change(struct request_queue *q, const char *name)
+{
+ int ret;
+
+ /* Protect q->elevator from elevator_init() */
+ mutex_lock(&q->sysfs_lock);
+ ret = __elevator_change(q, name);
+ mutex_unlock(&q->sysfs_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL(elevator_change);
+
+ssize_t elv_iosched_store(struct request_queue *q, const char *name,
+ size_t count)
+{
+ int ret;
+
+ if (!q->elevator)
+ return count;
+
+ ret = __elevator_change(q, name);
+ if (!ret)
+ return count;
+
+ printk(KERN_ERR "elevator: switch to %s failed\n", name);
+ return ret;
+}
+
+ssize_t elv_iosched_show(struct request_queue *q, char *name)
+{
+ struct elevator_queue *e = q->elevator;
+ struct elevator_type *elv;
+ struct elevator_type *__e;
+ int len = 0;
+
+ if (!q->elevator || !blk_queue_stackable(q))
+ return sprintf(name, "none\n");
+
+ elv = e->type;
+
+ spin_lock(&elv_list_lock);
+ list_for_each_entry(__e, &elv_list, list) {
+ if (!strcmp(elv->elevator_name, __e->elevator_name))
+ len += sprintf(name+len, "[%s] ", elv->elevator_name);
+ else
+ len += sprintf(name+len, "%s ", __e->elevator_name);
+ }
+ spin_unlock(&elv_list_lock);
+
+ len += sprintf(len+name, "\n");
+ return len;
+}
+
+struct request *elv_rb_former_request(struct request_queue *q,
+ struct request *rq)
+{
+ struct rb_node *rbprev = rb_prev(&rq->rb_node);
+
+ if (rbprev)
+ return rb_entry_rq(rbprev);
+
+ return NULL;
+}
+EXPORT_SYMBOL(elv_rb_former_request);
+
+struct request *elv_rb_latter_request(struct request_queue *q,
+ struct request *rq)
+{
+ struct rb_node *rbnext = rb_next(&rq->rb_node);
+
+ if (rbnext)
+ return rb_entry_rq(rbnext);
+
+ return NULL;
+}
+EXPORT_SYMBOL(elv_rb_latter_request);